Gti 8v

I have put a 1983 gti 8v engine into a vw caddy and it runs up fine and revs fine but when driving or putting it under load the engine has no power I have replaced all the electrics when converted and used a caddy sport fuel pump but am not sure if the pump is powerfull enough ? Can anyone help or got any ideas ? Thanks

The pump is the same as the GTI pump so you should have no issues (assuming its in good condition). Could it be something as simple as ignition timing or mixture?

Is there a way to do the ignition timing ? As I have tried rotating the distributer and it dosnt make a dufference and can't understand y it revs fine untill it's under load ? Thanks